Quinolones have been shown to be effective to varying degrees against a range of bacterial pathogens. However, as diseases caused by these pathogens are on the rise, there exists a need for antimicrobial compounds that are more potent than the present group of quinolones.
Gemifloxacin mesylate (SB-265805) is a novel fluoroquinolone useful as a potent antibacterial agent. Gemifloxacin compounds are described in detail in patent application PCT/KR98/00051 published as WO 98/42705. Patent application EP 688772 discloses novel quinolone(naphthyridine)carboxylic acid derivatives, including anhydrous (R,S)-7-(3-aminomethyl-4-methoxyiminopyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid of formula I.

PCT/KR98/00051 discloses (R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid methanesulfonate and hydrates thereof including the sesquihydrate.
I. Pneumococcal Pathogens
The incidence of pneumococci resistant to penicillin G and other β-lactam and non-β-lactam compounds has increased worldwide at an alarming rate, including in the U.S. Major foci of infections currently include South Africa, Spain, Central and Eastern Europe, and parts of Asia (P. C. Appelbaum, Clin. Infect. Dis. 15:77-83, 19929 Friedland, et al. Pediatr. Infect. Dis. 11:433-435, 1999; Friedland, et al., N. Engl. J. Med. 331:377-382, 1994; Jacobs, et al., Clin. Infect. Dis. 15:119-127, 1992 and Jacobs, et al., Rev. Med. Microbiol. 6:77-93, 1995). In the U.S. a recent survey has shown an increase in resistance to penicillin from <5% before 1989 (including <0.02% of isolates with MICs ≧2.0 μg/ml) to 6.6% in 1991-1992 (with 1.3% of isolates with MICs ≧2.0 μg/ml) (Brieman, et al., J. Am. Med. Assoc. 271:1831-1835, 1994). In another more recent survey, 23.6% (360) of 1527 clinically significant pneumococcal isolates were not susceptible to penicillin (Doern, et al., Antimicrob. Agents Chemother. 40:1208-1913, 1996). It is also important to note the high rates of isolation of penicillin intermediate and resistant pneumococci (approximately 30%) in middle ear fluids from patients with refractory otitis media, compared to other isolation sites (Block, et al., Pediatr. Infect. Dis. 14:751-759, 1995). The problem of drug-resistant pneumococci is compounded by the ability of resistant clones to spread from country to country, and from continent to continent (McDougal, et al., Antimicrob. Agents Chemother. 36:2176-2184, 1992: Munoz, et al., Clin. Infect. Dis. 15:112-118, 1992).
There is an urgent need of oral compounds for out-patient treatment of otitis media and respiratory tract infections caused by penicillin intermediate and resistant pneumococci (Friedland, et al., Pediatr. Infect. Dis. 11:433-435, 1992; Friedland, et al., N. Engl. J. Med. 331:377-382, 1994; M. R. Jacobs, Clin. Infect. Dis. 15:119-127, 1992; and Jacobs, et al., Rev. Med. Microbiol. 6:77-93, 1995). Available quinolones such as ciprofloxacin and ofloxacin yield moderate in vitro activity against pneumococci, with MICs clustering around the breakpoints (Spangler, et al., Antimicrob. Agents Chemother. 36:856-859, 1992; and Spangler, et al., J. Antimicrob. Chemother. 31:273-280, 1993). Genifloxacin (SB 265805)(LB 20-304a) is a new broad-spectrum fluoronaphthyridone carboxylic acid with a novel pyrrolidone substituent (Cormican, et al., Antimicrob. Agents Chemother, 41:204-211, 1997; Hohl, et al., Clin. Microbiol. Infect. 4:280-284, 1998; and Oh, et al., Antimicrob. Agents Chemother. 40:1564-1568, 1996). Previous preliminary studies (Cormican, et al., Antimicrob, Agents Chemother, 41:204-211, 1997; Hohl, et al., Clin. Microbiol. Infect. 4:20-9284, 1998: and Oh, et al., Antimicrob. Agents Chemother. 40:1564-1568, 1996) have shown that this compound is very active against pneumococci. This study further examined the antipneumococcal activity of gemifloxacin compared to ciprofloxacin, levofloxacin, sparfloxacin, grepafloxacin, trovafloxacin, amoxicillin, cefuroxime, azithromycin and clarithromycin by i) agar dilution testing of 234 quinolone susceptible and resistant strains; ii) examination of resistance mechanisms in quinolone resistant strains; iii) time-kill testing of 12 strains; iv) examination of the post-antibiotic effect (herein “PAE”) of drugs against 6 strains.
Provided herein is a significant discovery made using a gemifloxacin compound against a range of penicillin susceptible and resistant pneumococci by agar dilution, microdilution, time-kill and post-antibiotic effect methodology. Against 64 penicillin susceptible, 68 intermediate and 75 resistant pneumococci (all quinolone susceptible), agar dilution MIC50/90 values (μg/ml) were as follows: gemifloxacin, 0.03/0.06; ciprofloxacin, 1.0/4.0; levofloxacin, 1.0/2.0; sparfloxacin, 0.5/0.5; grepafloxacin. 0.125/0.5: trovafloxacin, 0125/0.25; amoxicillin, 0.016/0.06 (penicillin susceptible), 0.125/1.0 (penicillin intermediate), 2.0/4.0 (penicillin resistant); cefuroxime, 0.03/0.25 (penicillin susceptible). 0.5/2.0 (penicillin intermediate), 8.0/16.0 (penicillin resistant); azithromycin. 0.125/0.5 (penicillin susceptible). 0.125/>128.0 (penicillin intermediate), 4.0/>128.0 (penicillin resistant); clarithromycin 0.03/0.06 (penicillin susceptible), 0.03/32.0 (penicillin intermediate), 2.0/>128.0 (penicillin resistant). Against 28 strains with ciprofloxacin MICs ≧8 μg/ml, gemifloxacin had the lowest MICs (0.03-1.0 μg/ml, MIC90 0.5 μg/ml), compared with MICs ranging between 0.25 to >32.0 μg/ml)(MIC90s 4.0->33.0 μg/ml) for the other quinolones. Resistance in these 28 strains was associated with mutations in parC, gyrA, parE, and/or gyrB or efflux, with some strains having multiple resistance mechanisms. For 12 penicillin susceptible and resistant pneumococcal strains (2 quinolone resistant), time-kill results showed that levofloxacin at the MIC, gemifloxacin and sparfloxacin at 2×MIC and ciprofloxacin, grepafloxacin and trovafloxacin at 4×MIC, were bactericidal after 24 h. Gemifloxacin was uniformly bactericidal after 24 h at ≦0.5 μg/ml. Various degrees of 90% and 99% killing by all quinolones was detected after 3 h. Gemifloxacin and trovafloxacin were both bactericidal at the microbroth MIC for the two quinolone resistant pneumococcal strains. Amoxicillin, at 2×MIC and cefuroxime at 4×MIC, were bactericidal after 24 h. with some degree of killing at earlier time periods. By contrast, macrolides gave slower killing against the 7 susceptible strains tested, with 99.9% killing of all strains at 2-4×MIC after 2 h. Post-antibiotic effects for 5 quinolone susceptible strains were similar (0.3-3.0 h) for all quinolones tested, and significant quinolone PAEs were found for the quinolone-resistant strain.
Also provided herein is a significant discovery made using a gemifloxacin compound against quinolone-resistant pneumococci, demonstrating the activity of the gemifloxacin compound used was superior to a number of quinolones as described in more detail herein. Gemifloxacin compounds are valuable compounds for the treatment of infections caused by a range of pneumococcal pathogens, including those resistant to usual oral therapy, thereby filling an unmet medical need.
II. Haemophilus Pathogens
Although development of an effective vaccine against Haemophilus influenzae type b has led to disappearance of this organism in many parts of the world, its place has been taken by untypeable H. influenzae strains. The latter organisms (followed by Streptococcus pneumoniae and Moraxella catarrhalis) are now considered to be the leading cause of acute exacerbations of chronic bronchitis, and an important cause, together with S. pneumoniae and M. catarrhalis, of acute otitis media, sinusitis and community-acquired respiratory tract infections (Fang, et al., Medicine (Baltimore) 69:307-316, 1990: Hoberman, et al. Pediatr. Infect. Dis. 10:955-962, 1996; Jacobs, et al., Antimicrob. Agents Chemother, In press; and Zeckel, et al. Clin. Ther. 14:214-229, 1992).
Current recommendations by the NCCLS for use of Haemophilus Test Medium (herein “HTM”) for Haemophilus susceptibility testing have been complicated by difficulty in commercial manufacture of this medium, and its short half-life when made in-house. Reliable Haemophilus susceptibility testing with HTM requires use of freshly made medium used within 3 weeks of making (Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, 3rd Edition, NCCLS, Wayne, Pa., 1997).
Previous preliminary studies have shown that this gemifloxacin is very active against Haemophilus and Moraxella (Cormican, et al., Antimicrob. Agents Chemother. 41:204-211, 1997; Hohl, et al., Clin. Microbiol. Infect. 4:280-284, 1998; and Oh, et al., Antimicrobial Agents Chemother. 40:1564-1568, 1996).
A further embodiment provided herein is based in part on a significant discovery made using a gemifloxacin compound against nine rare clinical strains of Haemophilus influenzae from Europe with increased ciprofloxacin MICs were tested for in vitro activity (MICs) of gemifloxacin (SB-265805), ciprofloxacin, levofloxacin, sparfloxacin, grepafloxacin and trovafloxacin and checked for mutations in gyrA, parC, gyrB and perE, demonstrating the activity of the gemifloxacin compound used was superior to a number of quinolones as described in more detail herein. Gemifloxacin compounds are valuable compounds for the treatment of infections caused by a range of Haemophilus influenzae strains, including those resistant to usual oral therapy, thereby filling an unmet medical need.